1. Graduate Research Assistant, Auburn Univ., 2314 Sybel Dr., Mobile, AL 36693.
2. Assistant Professor, Auburn Univ., 221 Harbert Engineering Center, Auburn, AL 36849 (corresponding author).
3. Gottlieb Associate Professor, Auburn Univ., 232 Harbert Engineering Center, Auburn, AL 36849.
4. Associate Professor, Auburn Univ., 224 Harbert Engineering Center, Auburn, AL 36849.